In a cellular type wireless communication system represented by a mobile telephone network, a plurality of wireless base stations that are arranged in a distributed manner constitute a wide service area. Each wireless base station forms a wireless cell that is a range where communication with the wireless base station can be performed and establishes wireless links with wireless terminals belonging to the wireless cell. Each wireless terminal connects to an upper level network, such as the Internet network, via a wireless base station and performs data communication with various types of server devices. Note that, in general, approximately one to six wireless cells are managed by each wireless base station.
In a cellular type wireless communication system, it is further possible to, using a handover (HO) function, switch wireless cells, to one of which a wireless terminal belongs. The handover function enables a wireless terminal to appropriately switch a wireless cell to which the wireless terminal belongs to a proper wireless cell even while the wireless terminal is moving and to continue data communication.
In a wireless communication system, due to influence of temporal or spatial bias in occurring traffic, complicated propagation characteristics of radio waves, movement of users, or the like, variation is likely to occur in the quality of a wireless link (hereinafter, simply referred to as wireless quality) between a wireless terminal and a wireless base station. As an example, when a movement of a wireless terminal causes a propagation environment of radio waves between the wireless terminal and a wireless base station to change from a state of having no obstacle therebetween (a line-of-sight (LOS) state) to a state of having an obstacle therebetween (a non-line-of-sight (NLOS) state), the wireless quality is highly likely to change extremely before and after the change in the propagation environment.
A rapid change in wireless quality becomes a cause of deterioration or a factor in denying an improvement in the quality of end-to-end communication between a wireless terminal and a server device. For example, when communication is performed using a Transmission Control Protocol (TCP), which is a representative communication protocol used in Internet networks, incapability of transmission rate control using TCP in efficiently following a rapid change in wireless quality may cause network congestion. In addition, a rapid change in wireless quality may also cause an issue in that a communication band in a communication section between a wireless base station and a wireless terminal (hereinafter, referred to as a wireless section) is not fully used.
In order to solve such issues, technologies for predicting wireless quality of a wireless terminal have been proposed.
A Patent Literature 1 (PTL1) discloses a technology of calculating a regression equation from time-series data of latest wireless environment values and, using the regression equation, calculating predicted values of wireless environment values. According to a method disclosed in PTL1, for a regression equation for obtaining predicted values of wireless environment values, for example, an Auto-regressive (AR) model is used.
A Patent Literature 2 (PTL2) discloses a technology of, based on present positional information and pre-registered radio strength distribution information, predicting radio strength in future communication. According to a method disclosed in PTL2, radio strength is predicted by downloading data indicating radio strength conditions concerning a train line that a user is to use into a mobile information terminal in advance and predicting a position that the terminal reaches.
A Patent Literature 3 (PTL3) discloses a technology of predicting a transition of a mobile terminal device to an incommunicable state by determining whether or not a latest position of the mobile terminal device and a time fall into a positional range and a period of time, respectively, defined by customary condition information. According to a method disclosed in PTL3, positional information and temporal information are stored every time a mobile terminal device is brought to an incommunicable out-of-service state. In addition, conditions resembling conditions estimated to reappear among past conditions causing occurrence of the out-of-service state are set as the customary condition information.
A Non-Patent Literature 1 (NPL1) discloses a technology of predicting a future value of a Signal-to-Noise Ratio (SNR) between nodes in an ad hoc network. According to a method disclosed in NPL1, first, changes of past SNRs are stored as training data. When an SNR is predicted, a pattern having a high degree of similarity to a latest change pattern of SNRs is specified out of past change patterns of SNRs included in the training data. After that, a future SNR value is predicted using the specified change pattern of SNRs.